Treatment of cotton with radiation polymerized acrylonitrile



3,109,703 TREATR ENT (BF COTTQN WITH RADIATION PQLYMERIZED ACRYLONITRILEJett C. Arthur, in, Metairie, and Robert J. Demint, New Orleans, La,assignors to the United States of America as represented by theSecretary of Agriculture No Drawing. Filed Apr. 8, 1960, Ser. No. 21,0672 Claims. (Cl. 204-158) (Granted under Title 35, U.S. Code (1952), sec.266) A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the World for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

This invention relates to the treatment of cotton with acrylonitrilemonomer and then to the radiation polymerization of the acrylonitrilemonomer and has as its objects modifications of the physical propertiesof cotton, particularly decreases in stillness, increases inelongationat-break, and other changes in related properties of thecotton fibers to impart new and desirable properties for use in finishedcotton products.

In the production of cotton products in recent years, chemicalmodifications of the physical properties of cotton fibers to give themnew and desirable properties have become major factors in cottonutilization. Cotton cellulose has very low chemical reactivity; and ineffecting chemical modifications of cotton, usually concentrated bases,high temperatures, high pressures, or catalysts must be used. In manymodifications there is probably little or no chemical reaction, but themodifying chemicals simply coat the fiber. Generally, many of thesechemical treatments of the cotton fibers greatly reduce their tensileproperties and are not as durable as the cotton. Much of the beneficialeifects of the chemical treatments may be lost during subsequent using,washing, and cleaning of the cotton products.

Our present invention is an improvement over these processes in thatacrylonitrile monomer is applied to the cotton fibers and the smallmolecules of the monomer penetrate through the outer wall and around thelumen of the fiber. Then when the treated cotton is irradiated with highenergy ionizing radiations, the monomer is polymerized to form highmolecular Weight polymer Within the outer Wall and the lumen. Theradiation polymerized acrylonitrile can not be extracted out of thefiber with N,N-dimethyl formamide, a commonly used solvent forpolyacrylonitrile. As shown by electron micrographs, the radiationpolymerized acrylonitrile is inside of the cotton fiber as contrastedwith the usual treatment which is outside of the fiber. Consequently,the treatment with radiation polymerized acrylonitrile is as durable asthe cotton.

We have discovered unexpectedly that this type of treatment withradiation polymerized acrylonitrile significantly decreases thestiffness of the cotton fibers and significantly increases theelongation-at-break of the cotton fibers while other importantproperties of the cotton are not significantly changed. For example,treated, irradiated cotton fiber containing about 24 percent radiationpolymerized acrylonitrile has an average stiffness of 44 grams per texas compared with raw, untreated fiber of 128 grams per tex and has anelongation-at-break of 23.4 percent as compared with raw, untreatedfiber of 13.7 percent. In chemically modified cotton products requiringimproved softness and drape, such as cotton fiber blankets and othercotton products, these changes in properties of cotton fibers due totreatment with radiation polymerized acrylonitrile have particular andimportant values.

A United States Patent 3,109,793 Patented Nov. 5, 1963 In general, theprocess of this invention is: carried out at room temperature bysubjecting cotton fiber immersed in an aqueous solution of acrylonitrileto high energy radiation. The radiation can be from any convenientsource, provided the source is capable of supplying the requisite dosagewhich is, for this reaction, at least about 800,000 roentgens.

The solubility of acrylonitrile in water is limited. It is desirable,therefore, for the purpose of insuring an adequate concentration ofaqueous acrylonitrile, to utilize the recognized hydrotropic effect ofcertain inorganic salts. Zinc chloride, magnesium chloride, the nitratesalts of these elements, as well as certain other inorganic salts, whendissolved in water, markedly enhance the solubility of acrylonitrile inthe resultant aqueous salt solution.

Subsequent to the irradiation step, which treatment polymerizes theacrylonitrile to a high molecular weight polymer within the outer walland the lumen of the cotton fiber, the cotton fibers are freed from theloosely adhering extraneous polymer outside the fiber by washing orextracting the fibers with a good solvent for acrylonitrile polymer.Dimethyl formamide or dimethyl sulfoxide are two such solvents. Theacrylonitrile polymer inside the fiber remains unaifected by washing orextraction of the fiber with a polymer solvent. A water wash, of thefibers, followed by drying of the fibers, completes the process.

The following examples illustrate our invention in greater detail:

EXAMPLE I Cotton fiber yarn (4 parts) was treated with an aqueoussolution containing 32 parts of acrylonitrile monomer, 54 parts of zincchloride, and 14 parts of water at room temperature by padding on of thesolution to give a twofold increase in weight of the original yarn. Thetreated yarn was then irradiated to a dosage of 800,000 roentgens byhigh energy gamma ionizing radiations from radioactive coba1t-60 toradiation polymerize the acrylonitrile monomer. Then loosely adheringpolymer was removed by overnight treatment of the yarn at 25 C. withN-N- dimethyl formarnide solvent. The yarn was then washed with waterand dried in a current of air at 2.5 C. The

effects of the treatment on the properties of cotton fiber.

containing radiation polymerized acrylonitrile as compared withuntreated, control yarns are shown in Table 1.

Table 1.-Efiect of Radiation Polymerization of Acrylonitrile With Cottonon Its Stifiness, Elongation-at- Break, and Related Properties 1 I Whereindicated, treating solution: 32 parts of acrylonitriie, 54 parts ofzinc chloride, and 14 parts of water; radiation dosage: 800,000roentgens from high energy gamma ionizing radiations from radioactivecobalt'00.

EXAMPLE II Cotton fiber yarn (4 parts) was treated with an aqueous wasextracted and dried as in Example 1.

7 temperature by padding on of the solution to give a twofold increasein weight of the original yarn. The treated yarn was then irradiated todosages ranging from zero to" tion-at-break, and other relatedproperties of the cotton fibers are shown in Table 2.

Table 2.Efiect of Radiation Dosage on Polymerization of AcrylonitrileMonomer With Cotton and on Its Stifiness, Elongation-at-Break, andRelated Properties 1 Dosage, 100,000 roentgens Property of yarn Polymercontent, percent 0 0 3. 6 12. 3 15. 9 26 25. 8 Average stifiness, g./tex141 129 121 101 83 38 43 Elongation-at-break, per- 1; 13.9 12. 6 13. 916. 5 24. 6 22. 9 Breaking strength, lb 10. 1 9. 8 8. 7 8. 5 9.1 8. 2 8.8 Yarn number, tex 241 248 256 276 300 398 401 Breaking stress, g./tex19. 0 17.9 15. 3 14.0 13.7 9. 3 9. 9 Breaking toughness, g./

tex 0. 79 0.74 0. 58 0. 63 0.73 0.70 0.73 Moisture regain, percent. 7. 67. 7 7. 5 7.1 7. 1 6. 5 6. 4

1 Where indicated, treating solution: 32 parts of acrylonitrile, 54parts of zinc chloride, and 14 parts of water. 2 Untreated, unlrradiatedyarn. Treated, unirradiated yarn.

EXAMPLE III solutions to give a two-fold increase in weight of theoriginal yarn. The treated yarn was then irradiated to a dosage of800,000 roentgensby high energy gamma ionizing radiations fromradioactive cobalt-60 to radiation polymerize the acrylonitrile monomer.

The effects of variations in concentrations of acrylonitrile and zincchloride on the amount of polymer formed in the cotton and therelationship of these quantities to stiffness, elongation-at-break, andother related properties of the cotton fibers are shown in Table 3.

The yarn Table '3.-Efiect of Reagent Concentration on Polymerization ofAcrylonitrile Monomer With Cotton and on Its Stiffness,Elongation-at-Break, and Related Properties 1 Treating Solutions 3Property of Yarn A B C C 3 D E Polymer content, percent 0. 03 4. 9 22. 80.0 3. 7 G. 3 Average stifiness, g./tex 134 89 45 129 76 88Elongation-at-break, percent 13.5 15.6 23. 2 13.9 18. 6 14.9 .Breakingstrength, lbs 10.1 '8. 0 8. 7 9. 8 8. 9 8.2 Yarn number, tex 252 281 379248 286' 283 Breaking stress, g./tex 18.1 13.9 10.4 17. 9 14.1 13.2Breaking toughness, gJtex 0. 77 0. 69 0.80 0.74 0.86 0.60

1 Radiation dosage: 800,000 roentgens from high energy gamma ionizingradiations from radioactive cobalt-60.

2 Treating solution A: 32 parts of acrylonitrile, 44 parts of zincchloride, and 24 parts of Water; B: 32, 51, 17; O: 32, 54, 14; D: 20,60, 20; E: 40, 45, 15, respectively.

3 Treated, um'rradiated yarn.

Weclaim:

1. A process comprising padding cotton fibers to a twofold wet pick-upwith an aqueous solution containing at least about 30 weight percent ofacrylonitrile monomer and at least about weight percent of an inorganicsalt for enhancing the solubility of the acrylonitrile in the resultingaqueous salt solution, irradiating the padded fibers to a dosage of atleast about 800,000 roentgens with high energy gamma ionizing radiationto polymerize the acrylonitrile monomer within the cotton fibers to theex tent that the irradiated fibers contain at least 20 weight percent ofacrylonitrile polymer within the fibers, and removing adheringacrylonitrile polymer from the surfaces of the irradiated cotton fibersthereby to obtain cotton fibers that exhibit decreased stiffness andincreased elongation-at-break as compared with untreated cotton fibers.

2. The process of claim 1 wherein the inorganic salt is zinc chloride.

References Cited in the file of this patent UNITED STATES PATENTS2,956,899

OTHER REFERENCES Chemistry and Industry (Apr. 6, 1957), page 412.Textile Research Journal, vol. XXIX, No. 9, September 1959, page 759.

1. A PROCESS COMPRISING PADDING COTTON FIBERS TO A TWOFOLD WET PICK-UPWITH AN AQUEOUS SOLUTION CONTAINING AT LEAST ABOUT 30 WEIGHT PERCENT OFACRYLONITRILE MONOMER AND AT LEAST ABOUT 50 WEIGHT PERCENT OF ANINORGANIC SALT FOR ENHANCING THE SOLUBILITY OF THE ACRYLONITRILE IN THERESULTING AQUEOUS SALT SOLUTION, IRRADIATING THE PADDED FIBERS TO ADOSAGE OF AT LEAST ABOUT 800,000 ROENTGENS WITH HIGH ENERGY GAMMAIONIZING RADIATION TO POLYMERIZE THE ACRYLONITRILE MONOMER WITHIN THECOTTON FIBERS TO THE EXTENT THAT THE IRRADIATED FIBERS CONTAIN AT LEAST20 WEIGHT PERCENT OF ACRYLONITRILE POLYMER WITHIN THE FIBERS, ANDREMOVING ADHERING ACRYLONITRILE POLYMER FROM THE SURFACES OF THEIRRADIATED COTTON FIBERS THEREBY TO OBTAIN COTTON FIBERS THAT EXHIBITDECREASED STIFFNESS AND INCREASED ELONGATION-AT-BREAK AS COMPARED WITHUNTREATED COTTON FIBERS.